As to its principle of operation the proposed semiconductor device is closest to varicaps (varactors), i.e., semiconductor devices with voltage-controlled reactance. It is common knowledge (cf. a textbook "Physics of semiconductor devices" by S. Zea, V.1, Moscow Mir Publishers, 1984, pp.80-91, 260-262, 381, 384 (in Russian) that in all the three basic elements of semiconductor electronics (that is, p-n junction, Schottky barrier, and MIS-structure) a semiconductor layer is liable to be formed at a definite polarity of the charge applied, said layer being depleted in majority charge carriers and serving as an analog of a dielectric interlayer in conventional capacitors. The thickness of the depletion layer depends on the bias voltage, whereby the differential capacitance C of a semiconductor device may be controlled by the voltage V.
A typical varactor construction appears as a plane-parallel heavily doped semiconductor layer having one conduction type and established in a weakly-doped working area having another conduction type. Both of the plates are provided with ohmic contacts for the control voltage to apply thereto. By varying the distribution of a dopant in the varactor operating area one can provide various C/U relationships. All and every of varicaps are disadvantageous in that the range of voltage values used is limited to the breakdown voltage of the depletion layer. Thus, the ratio between the maximum and minimum capacitance values is restricted too the breakdown voltage in an overwhelming majority of constructions of the now existing varactors.
A variable capacitor of the heretofore-known construction is now in widespread use (cf., e.g., A reference guide to high-frequency circuitry, by E.Red, Moscow Mir Publishers, 1990, pp.219-220 (in Russian), which appears as a mechanical device adapted to displace the capacitor plates with respect to each other. An obvious disadvantage of the device resides in sluggishness of mechanical functioning.
Microwave-frequency microelectronics make use most frequently of a stripline which is in fact a twin line, comprising two conductor strips between which an insulator or semi-insulator layer is placed (cf., e.g., "Electronics". An Encyclopaedic Dictionary, Moscow, Sovetskaya Entsiklopedia Publishers, 1991, pp.253, 254, 491; Modern Gallium-Arsenide Based Devices by M.Shur, Moscow Mir Publishers, 1991, p.405 (in Russian).
A disadvantage inherent in all transmission lines mentioned before resides in that such line parameters as characteristic impedance and length cannot be controlled by an external voltage source which impedes microminiaturization, adjustment and frequency retuning of numerous micrcowave-frequency microelectronic devices.
A transistor is commonly understood to mean a semiconductor device having three or more leads for applying the control voltage thereto and adapted for amplifying, generating, and converting electric oscillations (cf. Encyclopaedic Dictionary, Moscow, Sovetskaya Entsiklopedia Publishers, 1991, p.557). A substantial disadvantage inherent in the now-existing transistors, both field-effect and bipolar junction ones, consists in that their output power is inversely proportional to the squared frequency thereof, which results from a limitation imposed by the avalanche-breakdown voltage of a rather narrow space-charge region of the p-n junction and by ultimate carrier velocity (cf. S. Zea, op. cit., pp.178-179).